Cyclone furnace



Sept. 4, 1962 o. ROSAHL 3,052,221

CYCLONE FURNACE Filed Sept. 27, 1955 2 Sheets-Sheet 1 FIG. 6

FIG. 3 INVENTOR.

Orro Rosahl ATTORNEY Sept. 4, 1962 o. ROSAHL 3,052,221

CYCLONE FURNACE Filed Sept. 27, 1955 2 Sheets-Sheet 2 FIGS FIG. 4

INVENTOR.

0H0 Rosahl United States Patent Oflice 3,052,221 Patented Sept. 4, 1962 3,052,221 CYCLONE FURNAE Otto Rosahl, ()herhausen, Germany, assignor to The Babcock & Wiicox Comp-any, New York, N.Y., a corporation of New Jersey Filed ept. 27, 1955, Ser. No. 537,064 6 Claims. (Cl. 122-235) This invention relates to a high capacity fluid heating unit having a plurality of cyclone furnaces so constructed as to present an arrangement resulting in improved circulatory characteristics for the cooling system.

More specifically, the invention is concerned with high capacity fluid heating installations having a fluid circulation system and including a lower and an upper cyclone furnace, with the longitudinal axis of the upper cyclone furnace arranged vertically spaced from and preferably parallel to the longitudinal axis of the lower cyclone furnace and with fluid cooling means extending uninterruptedly upwardly to form the circumferential walls of both the lower and upper cyclone furnaces.

Another object is the provision of a fluid heating unit having a lower cyclone furnace arranged with its main axis in a substantially horizontal position and an upper cyclone furnace arranged with its main axis parallel to and vertically spaced from the main axis of the lower cyclone furnace and which is further characterized by a special arrangement of furnace slag outlets.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which certain specific embodiments of the invention are illustrated and described.

Of the drawings:

FIG. 1 is a sectional elevation of a cyclone furnace fired fluid heating unit constructed in accordance with the invention;

FIG. 2 is a front view, partly in section, of the apparatus shown in FIG. 1;

FIG. 3 is a sectional view showing a modified arrangement of fluid cooled tubes extending from the lower cyclone furnace to the upper cyclone furnace;

FIG. 4 is a fragmentary sectional plan view showing another modified arrangement of fluid cooled tubes extending from the lower cyclone furnace to the upper cyclone furnace;

"FIG. 5 is a sectional front view taken on the line 44 of FIG. 4; and

FIG. 6 is a schematic view showing an improved arrangement of slag outlets for a pair of superposed cyclone furnaces.

While various kinds of liquid and gas fuels can be burned in the cyclone furnace construction illustrated, the constructions illustrated and hereinafter described are especially designed and particularly adapted for burning coarsely pulverized or granulated bituminous or semibituminous coal; and although the invention is illustrated as embodied in a natural circulation fluid heating unit, the invention in its broader aspects may be carried out in a forced flow fluid heating unit.

The main portions of the unit illustrated include a fuel firing section consisting of a plurality of independently operable superposed cyclone furnaces 10 and 12 of relatively small volume and boundary wall area arranged to burn a solid fuel at high rates of heat release and separately discharging high temperature gaseous products f combustion and separated ash residue as a molten slag into a primary furnace chamber 14, from which the molten slag drains through a floor opening 16 into a slag pit 18. The heating gases with a small amount of molten ash in suspension are directed downwardly by a reflecting arch 20 and then pass upwardly through a slag collecting screen 22 into a vertically elongated radiation and gas mixing chamber 24 of rectangular cross-section, the walls of which include wall tubes such as '26 and 28 connected into the natural circulation system of the unit. The heat ing gases from the chamber 24 leave the upper rear side thereof and flow horizontally through a convection heating chamber 30 of rectangular vertical cross-section, of which only a portion is shown.

The high capacity natural circulation fluid heating unit illustrated has a fluid circulation system which includes an upper rear drum 32; steam circulators 34 and water circulators 36 connecting drum 32 to a main steam and water drum 38, from which steam passes through supply tubes, not shown, to a superheater inlet header; downcomer pipes 40 located at opposite sides of the unit, each pipe having tubes 42 extending fro-m its upper end to the water space of drum 38 and tubes 44 and 46 extending from its lower end to a drum 48 and a cyclone furnace supply header 50, respectively. All of the primary furnace chamber 14, chamber 24 and screen 22 fluid heating circuits receive water from the drum 48 and discharge a steam and water mixture to the drum 32.

'In accordance with my invention the fluid heating unit is fired by an upper and a lower cyclone type furnace of the general character described in U. S. Patent 2,594,312, with the longitudinal axis of the upper cyclone furnace vertically spaced from and preferably parallel to the longitudinal axis of the lower cyclone furnace. Each of the cyclone furnaces is of horizontally elongated circular cross-section, the furnace chamber being formed by closely spaced studded tubes covered by a layer of suitable refractory material. The front end of each cyclone furnace is provided with a rearwardly flaring frusto-con ical section. T he rear end of the furnace is partly closed by a vertical fluid beating wall 52 having a gas outlet 54 in the form of a rcentrant throat 56 arranged therein concentric with the furnace chamber axis. Coarsely pulverized or granulated bituminous or semi-bituminous coal, carried in a stream of preheated primary air and supplied through conduits 58 is introduced tangentially through fuel inlets 60 along the length of each cyclone furnace. Streams of secondary air are admitted tangentially through secondary air ports 62 along the length of each cyclone furnace in the same direction of rotation and at the outer side of the streams of fuel laden air discharging from the fuel inlets 60. The high velocity of the burning fuel and air causes the gas stream to follow a helical path toward the rear of each furnace where the gas is caused to reverse direction before ent ring the throat 56. A relatively small amount of fly ash and molten particles is normally present in suspension in the outgoing gases, and this residue is largely separated in the primary furnace chamber 14. Molten slag resulting from combustion continually discharges through an opening 64 at the rear of each cyclone furnace and flows down to a slag pool on the floor of the primary furnace chamber 14, whence it is continuously drained through the floor opening 16 into the slag pit 18, along with ash and slag particles which may be separated in the primary furnace chamber.

Heretofore, in vapor generating units having a plurality of horizontally arranged cyclone furnaces mounted at different elevations in the same wall, the practice has been to connect the lower ends of the fluid cooled tubes forming the circumferential wall of each cyclone furnace to a separate supply header and the upper ends to a separate discharge header, with tubes connecting each of the supply headers to the lower Water drum and each of the discharge headers to the steam and water drum, thus defining parallel flow paths for Water flow to the respective cyclone furnaces.

It also has been customary to expose a portion of the length of the riser tubes extending between each cyclone furnace discharge header and the steam and water drum to the heat of the gases to promote effective circulation in the tubes constituting a part of each cyclone furnace. This arrangement is particularly adapted to promote circulation in the tubes of an out-of-service cyclone furnace while other cyclone furnaces associated with the same fluid heating unit are operating at maximum heat input.

In accordance with the present invention, in a fluid heating unit having a lower and an upper cyclone furnace, with the longitudinal axis of the upper cyclone furnace arranged vertically spaced from and preferably parallel to the longitudinal axis of the lower cyclone furnace, the fluid cooled tubes forming the circumferential wall of the lower cyclone furnace are extended uninterruptedly upwardly to form the circumferential wall of the upper cyclone furnace. With this arrangement there is continuous and effective fluid circulation in the wall tubes of each cyclone furnace under all operating conditions, without the use of headers between cyclone furnaces and without exposing portions of the riser tubes extending between the discharge header and the main steam drum to the heat of the gases. The elimination of headers between the upper and lower cyclone furnaces also makes possible a more compact arrangement of cyclone furnaces.

As shown in FIG. 2, the curved peripheral wall of each furnace chamber is defined by oppositely curved rows of fluid cooled tubes 66 and 68 extending between the supply header 50 and a discharge header 7 0. In the lower cyclone furnace 10 wall tubes 68 along one side are bent radially outwardly along an involute curve for a major portion of the furnace chamber length, while the corresponding tubes 66 along the opposite side are bent into transversely spaced horizontally aligned tube groups to define a series of side by side openings for the secondary air ports 62 and the fuel inlets 60. The tubes 66 and 68 are then extended uninterruptedly upwardly to define the curved peripheral wall and fuel and air inlets of the upper cyclone furnace 12, with each tube bent into substantially the same form and associated with the same curved wall portion as in the lower cyclone furnace. Riser tubes 72 extending upwardly outside the wall 28 connect the discharge header 70 to the drum 32. Recirculation tubes 74 located outside the heat connect headers 50' and 70 and serve to promote effective circulation in the tubes defining the cyclone furnace walls and to reduce the area of the supply and riser tubes.

Uniform distribution of fluid to the cyclone furnace tubes is essential to efficient operation. The arrangement of the cyclone furnace circulation system may be affected by such factors as a non-uniform heat absorption pattern over the length of tube exposed to furnace temperature and unequal resistance losses due to fluid friction, turbulence and acceleration. The described cyclone furnace circulation system may be altered as hereinafter indicated to compensate for such variations.

As illustrated in FIG. 2, the supply header 50 and discharge headers 70 are subdivided by longitudinally extending internal diaphragms 76 to group the wall tubes 66 and 68 into separate circuits, with each circuit provided with a sufficient number of supply and riser tubes to assure uniform distribution of fluid.

In the modified construction shown in FIG. 3 the openings for fuel and air in the lower cyclone furnace are arranged on one side and the corresponding openings in the upper cyclone furnace are arranged on the opposite side by suitably bending the fluid cooled tubes. With the openings so arranged, the gas whirls in the lower cyclone furnace have a rotational direction opposite to the gas whirls in the upper cyclone furnace. With this construction each fluid cooled tube extending between the headers i 50 and 70 has substantially the same length and the same number and form of bends. Moreover, the heat absorption pattern over the length of tube exposed to furnace temperature is uniform.

In the modification illustrated in FIGS. 4 and 5, the transition of the fluid cooled tubes from the lower to the upper cyclone furnace is made by criss-crossing the tubes, with the exception of closure tubes 68a forming the front and rear boundary walls of the entrance for fuel and air which are continued upwardly along the same side in the upper cyclone furnace as in the lower cyclone furnace. Opposite tubes at the transition point above the lower cyclone furnace are crossed so that the wall tubes forming one side of the lower cyclone furnace form the opposite side wall in the upper cyclone furnace. The crossing at the circumferential wall portion used for the entrance of fuel and air is made by bending the wall tubes 66 along one side of the lower cyclone furnace into transversely spaced horizontally aligned tube groups, while reversely bending the corresponding tubes 68 along the opposite sides, thus defining the air and fuel inlets 6t and 62 for the lower cyclone furnace. The air and fuel inlets for the upper cyclone furnace are defined in the same manner as shown in FIG. 2 and as hereinbefore described. With this arrangement each fluid cooled tube extending between the headers 50 and 70 has substantially the same length and the same number and form of bends.

Heretofore it has been customary to remove the molten slag collecting in the bottom of the cyclone furnace through a slag outlet arranged in the gas outlet end. This arrangement may present some difficulty in a fluid heating unit fired by a pair of superposed cyclone furnacm, each furnace having its major axis arranged substantially horizontal, in that the flow of slag from the upper furnace chamber may be disturbed by the heating gases discharging from the gas outlet of the lower furnace chamber, causing dispersion of the slag stream and resulting in carryover and deposition of chemicals in the convection passes of the fluid heating unit. While the amount of such deposits is relatively small, the arrangement of slag outlets shown in FIG. 6 eliminates the possibility of such a difliculty. As illustrated, each of the cyclone furnaces is of horizontally elongated substantially circular crosssection with its major axis arranged horizontal and with fuel and air inlets 6t) and 62 tangentially arranged with respect to the circumferential wall along a major portion of the furnace length. A slag outlet 73 arranged in the bottom portion of the circumferential wall of the cyclone furnace 12 is connected by a conduit to a slag inlet 82 arranged in the top portion of the circumferential wall of the lower cyclone furnace 10. A slag outlet 84- arranged in the bottom portion of the circumferential wall of the lower cyclone furnace 10 is connected to an auxiliary slag pit, not shown, or to the slag pit 18 by a conduit 86, of which only a portion is shown. The slag discharging from the outlet 78 flows through the conduit 80 and inlet 82 into the lower cyclone furnace 10. The slag discharging into the cyclone furnace 10 merges with the slag coat ing on the walls thereof and the resulting stream is discharged through the slag outlet 84 and conduit 36 into the auxiliary slag pit or the slag pit 18.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage Without a corresponding use of the other features.

What is claimed is:

1. A fluid heating unit having fluid circulation system and comprising a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace, each of said cyclone furnaces having an elongated combustion chamber of circular transverse crosssection arranged with its longitudinal axis horizontal, means forming a restricted gas outlet at one end of each of said cyclone furnaces, means for burning a slag-forming solid fuel in said cyclone furnaces under a mean furnace temperature above the fuel ash fusion temperature, walls defining a chamber arranged to receive high temperature heating gases from said combustion chambers, fluid cooled tubes etxendin g uninterruptedly upwardly to form the circumferential wall of each cyclone furnace, means connecting said fluid cooled tubes into said fluid circulation system, a slag outlet in the bottom portion of each combustion chamber extending through the circumferential wall thereof, a slag inlet in the top portion of the lower cyclone furnace combustion chamber extending through the circumferential wall thereof, and means establishing communication between said slag outlet of the upper cyclone furnace and said slag inlet of the lower cyclone furnace.

2. In combination, a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace, each cyclone furnace having walls defining a combustion chamber of substantially circular crosssection arranged with its longitudinal axis substantially horizontal, fluid cooling means for said walls, means forming a restricted gas outlet at one end of each of said cyclone furnaces, means for burning a slag-forming solid fuel in said cyclone furnaces under a mean furnace temperature above the fuel ash fusion temperature, a slag outlet in the lower portion of each combustion chamber extending through the circumferential Wall thereof, a slag inlet in the upper portion of the lower cyclone furnace combustion chamber extending through the circumferential wall thereof, and means establishing communication between said slag outlet of the upper cyclone furnace and said slag inlet of the lower cyclone furnace.

3. In combination, a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace and vertically aligned therewith, each cyclone furnace having walls defining a combustion chamber of substantially circular cross-section arranged with its longitudinal axis substantially horizontal, fluid cooling means for said walls, means forming a restricted gas outlet at one end of each of said cyclone furnaces, means for burning a slag-forming solid fuel in said cyclone furnaces under a mean furnace temperature above the fuel ash fusion temperature, a slag outlet in the lower portion of each combustion chamber extending through the circumferential wall thereof, a slag inlet in the upper portion of the lower cyclone furnace combustion chamber extending through the circumferential wall thereof, and means establishing communication between said slag outlet of the upper cyclone furnace and said slag inlet of the lower cyclone furnace.

4. In combination, a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace and vertically aligned therewith, each cyclone furnace having walls defining a combustion chamber of substantially circular cross-section arranged with its longitudinal axis horizontal, fluid cooling means for said walls, means forming a restricted gas outlet at one end of each of said cyclone furnaces, mean for burning a slag-forming solid fuel in said cyclone furnaces under a mean furnace temperature above the fuel ash fusion temperature, a slag outlet in the lower portion of each combustion chamber extending through the circumferential wall thereof, a slag inlet in the upper portion of the lower cyclone furnace combustion chamber extending through the circumferential wall thereof, said slag outlets and inlet being vertically aligned, and means establishing corrnnunication between said slag outlet of the upper cyclone furnace and said slag inlet of the lower cyclone furnace.

5. In combination, a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace and vertically aligned therewith, each cyclone furnace having walls defining a combustion chamber of substantially circular cross-section arranged with its longitudinal axis horizontal, fluid cooling means for said walls, means forming a restricted gas outlet at one end of each of said cyclone furnaces, means for burning a slag-forming solid fuel in said cyclone furnaces under a mean furnace temperature above the fuel ash fusion temperature, said fuel burning means including axially elongated combustion air and fuel inlets arranged tangentially of the circumferential wall of each combustion chamber, a slag outlet in the lower portion of each combustion chamber extending through the circumferential wall thereof, a slag inlet in the upper portion of the lower cyclone furnace combustion chamber extending through the circumferential wall thereof, said slag outlets and inlet being vertically aligned, and means establishing communication between said slag outlet of the upper cyclone furnace and said slag inlet of the lower cyclone furnace.

6. In combination, a lower cyclone furnace, an upper cyclone furnace arranged with its longitudinal axis vertically spaced from the longitudinal axis of the lower cyclone furnace, each cyclone furnace having walls defining a combustion chamber of substantially circular cross-section, fluid cooling means for said walls, means forming a restricted gas outlet at one end of each of said cyclone furnaces, means for initating the burning of a slag-forming "solid fuel in each of said cyclone furnaces under a mean furnace temperature above the fuel ash fusion tem perature, a slag outlet in the lower portion of each combustion chamber for the discharge of molten slag, a slag inlet in the lower combustion chamber, and means establishing communication between said slag outlet of the upper combustion chamber and said slag inlet of the lower combustion chamber, said last named means being constructed and arranged so that the slag discharging from the upper combustion chamber to the lower combustion chamber is out of contact with the gases discharging from the gas outlet of the lower combustion chamber.

References \Cited in the file of this patent UNITED STATES PATENTS 2,355,892 Praeger Aug. 15, 1944 FOREIGN PATENTS 512,102 Belgium June 30, 1952 701,142 Great Britain Dec. 16, 1953 1,062,578 France Dec. 9, 1953 

